Circuit breaker



26, 1952 H: D. DORFMAN ET AL 2,608,629

CIQRCUIT BREAKER Filed April 25, 1950 Fig.l.

6? Insulation 59 I3 INVENTOR$ Hiiler flDofimmw and wiliiem D. Pmfon.

WITNESSES:

Patented Aug. 26, 1952 CIRCUIT BREAKER Hiller l). Dorfman and William D. Patton, Beaver,

Pa., assigncrs to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application April 25', 1950, Serial No. 157,866

6 Claims.

This invention relates to circuit breakers, and more particularly to circuit breakers for controlling lighting and moderate power circuits.

An object of the invention is to provide a circuit breaker embodying an improved thermally and magnetically responsive trip device having the magnetically responsive means supported entirely on the thermally responsive means.

Another object of the invention is to provide an improved thermally and magnetically responsive trip device wherein operation of the magnetically responsive element applies no bending stress to the thermally responsive elementand avoids the possibility of the thermally responsive element taking a permanent set due to its being bent when in a heated condition.

Another object of the invention is to provide a trip device having electroresponsive means energized by current flowing through a thermally responsive element and having an armature movable against the bias of a spring other than the thermally responsive element to permit the use of a stiffer thermal element without requiring a large magnetic force for magnetic tripping.

Another object of the invention is to provide a circuit breaker which is simple, safe and reliable in operation, and which is inexpensive to manufacture.

The novel features that are considered char acteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawing.

In said drawing,

Figure 1 is a side elevational view, partly in section, of a circuit breaker embodying the principles of the invention.

Referring to Fig. l of the drawing, the circuit breaker is of the three-pole type and is mounted in a housing comprising a base I I and. a removable cover I3, both of molded insulating material. Each pole of the breaker (only the center pole being shown) includes a stationary contact IQ, an 'arc extinguisher 2|, and a movable contact 23. 'The stationary contact i9 is mounted on the inner end of a strip 25 of conducting material, the other end of which is secured to a terminal 21.

The movable contact 23 is carried on the free end of a spring contact arm 29 which is secured to a U-shaped switch member 3|. The movable contact 23 is electrically connected by means of a flexible conductor 33, to the current responsive trip means of the trip device which will be hereinafter described. The current responsive trip means is, in turn, connected to a conducting strip 35 having a terminal 31 secured to the outer end thereof. The contacts, switch members and tripmeans for the three poles of this breaker are of substantially identical construction; hence only one pole has been shown and described.

The three movable switch members 3| are mounted for simultaneous movement about a common axis by means of a sectional pivot shaft 39, the center section of which is supported in the side walls of a U-shaped frame 4| secured to the base I I of the breaker. The switch members 3| of the outer poles (not shown) are secured to the outer sections of the pivot shaft 39, and are mechanically connected to the center pole switch members, but insulated therefrom, by insulating connecting hubs 43 (only one being shown) which connect the three separate sections of the pivot shaft together. A stop pin 45 extending through the frame 4| cooperates with projections formed on the center pole switch member 3| to limit the opening movement of the assemblage of switch members.

A single operating mechanism is provided for simultaneously actuating the switch members of all three poles of the breaker to open and closed positions. The operating mechanism is mounted in the frame 4|, and comprises a U-shaped operating member 41 having its legs pivoted on pivot members 49 struck out from the frame 4|, a releasable carrier lever 5| pivoted on a pivot pin 53 in the frame 4|, a pair of toggle links 55 and 51', and overcenter springs 59 (only one being shown). The toggle links 55 and 51 are pivotally connected together by means of a knee pivot pin 8|. The inner toggle link 55 is pivotally connected by a pivot pin 63 to the center pole switch member 3!. The toggle link 51 is pivotally connected at its outer end by a pivot pin 35 to the releasable carrier lever 5|. The overcentcr springs 59 have their outer ends connected to the bight portion of the U-shaped operating member 7, and their inner ends are connected to the knee pivot pin 6| of the toggle ii5'|. An operating handle '6'! of molded insulating material is secured to the outer end of the operating member 41. The operating handle 61 is provided with a handle portion which extends through an opening 69 in the cover I3.

/ The operating handle is also provided with an arcuate portion H which serves to substantially close the opening 69 in all positions of the handle. Lugs Hare struck out from the sides of the frame 4! to limit the opening and closing movements of the operating member 41.

The breaker contacts are manually opened by clockwise movement of the operating handle from the position in which it is shown in Fig. 1. This movement carries the line of action of the overcenter springs 59 across to the right of the pivot pin 65 whereupon the force of the springs causes collapse of the toggle 55-51 thereby moving the movable contacts to the open position with a snap action. The contacts are closed by counterclockwise movement of the handle back to the Fig. 1 position. This moves the line of action of the springs 59 across to the left of the pivot pin 65, at which time the springs actuate the toggle 55-5'l to its extended overset position shown, thereby moving the movable contacts to the closed position with a snap action.

The trip device of the circuit breaker includes a latch 13 pivotally mounted on a pivot pin 15 supported in the frame 4|. Anextension 19 of the latch is provided with an opening Bl, one edge of which engages the free end of the carrier lever '51 and releasably restrains the carrier in normal position. The latch 13 is also provided with an extension 83 having an opening 85 thereon. A trip bar 81 of molded insulating material, and common to all of the poles of the breaker,.is mounted for rotation by means of a shaft 89 molded therein, the ends of which are mounted in brackets 5-! (only one being shown) secured to the base i l of the housing. An arcuate latch member 93 is molded into the trip bar in alignment with the opening 85 in the latch member 13. In the latching position of the parts, the carrier 51 is latched by the main latch 13 which, in turn, is held in latching position by the latch member 93. A spring 95 coiled about the pivot pin 15 biases the latch member 73 in unlatching direction and also biases the trip bar 81 to latching position. The trip bar 81 is provided with a plurality of projections 91, one for each pole of the breaker, molded integral therewith.

Each pole of the breaker is provided with an overload trip device including a bimetal element |Dl having a mounting foot formed at right angles thereto by which the bimetal element is secured to the base I l of the breaker, the mounting foot being secured by means of a screw I03 to a metal insert E35. At its free end, the bimetal element carries an adjusting screw I01 having a rounded inner end for engaging the projection 91 and operating the trip bar 81' upon deflection of the bimetal element. The free end of the bimetal element ID! is electrically connected to the conducting strip 35 by a flexible conductor I09, and the flexible conductor 33 connects the foot of the bimetal element to the movable contact as shown in Fig. 1. A U-shaped magnet yoke H! is rigidly secured to the bimetal element by means of a rivet H3 which also serves to secure the lower end of an armature support spring 1 !5 to the opposite side of the bimetal element. The spring I i5 is formed away from the bimetal element H]! and has an armature i ll secured thereto, near its upper end, by means of a rivet H9. In its normal unattracted position, the armature l I! lies substantially parallel to the bimetal element Hll and has an angle l2! formed at its upper end adapted to engage the projection 9'! on the trip bar. The magnet yoke i H is provided with pole pieces having sloping pole faces I23 thereon against which the armature is attracted upon energization of the magnet yoke.

The bimetal element Hil deflects toward the left when heated a predetermined amount in response to an overload current below a predetermined value-and the rounded'end of the screw I81 engages and actuates the trip bar-to trip the breaker in the manner previously described.

When an overload current of, for instance, 100% or more of normal rated current flows through bimetal element IBI, the armature HT is instantaneously attracted against the pole faces The slope of the pole faces is such that when the armature is moved thereagainst, it pivots substantially about the upper projecting ends thereof and causes the angular portion l2! of the armature to engage the projection 91 and instantaneously actuate the trip bar 81 to trip the breaker. Upon deenergization of the electromagnet, the armature mounting spring H5 restores the armature to the unattracted position shown in Fig. 1.

Following an automatic opening operation of the breaker, the carrier lever 5| must be reset to the latched position before the breaker contacts can be closed. This is effected by clockwise movement of the handle to a position slightly beyond the off position. During this movement, a projection 99 on the operating member 4'! engages and moves the carrier lever 5i back to the latching position. During the latter part Of the resetting movement, the free end of the carrier lever 51 moves into the opening 8| in the latch member 13 and restores this latch to latching position. The spring 95 then returns the trip bar 8'! to its latching position shown. The circuit breaker may then be closed by movement of the handle to the on position in the previously described manner.

From the foregoing, it will be seen that there is provided an improved circuit breaker of simple and inexpensive construction wherein the operation of the magnetic trip element applies no bending stress to the thermal element and avoids the possibility of the thermal element taking a permanent set due to its being stressed when in a heated condition, and in which the tripping armature is movable against the bias of a spring other than the thermal element, so that a stifier bimetal element may be used without requiring a greater magnetic force for magnetic tripping.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it y is to be understood that various changes in the structural details and arrangement of parts thereof may be made without departing from some of the essential features of the invention. I

We claim as our invention:

1. A circuit breaker having relatively movable contact means and a releasable member operable when released to effect opening of said contact means, a trip member operable to effect re lease of said releasable member, current responsive means for effecting release of said releasable member in response to overload currents below a predetermined value comprising a bimetal element, a U-shaped magnetic member rigidly mounted on said bimetal element, the legs of said U-shaped magnet yoke having sloping pole faces. a floating armature resiliently mounted on said bimetal element having an end disposed adjacent said trip member and the other end adapted to be attracted against said pole faces in response to overload currents above said predetermined value, and said armature when attracted against said pole faces pivoting about the ends of said legs and causing said one end thereof to engage and operate said trip member.

2. A circuit breaker having relatively movable contact means and a member releasable to effect opening of said contact means, a trip member operable to effect release of said releasable member, current responsive means comprising a bimetal element operable when heated a predetermined amount in response to overload currents below a predetermined value to engage and actuate said trip member, a magnet yoke rigidly secured to said bimetal element and provided with pole pieces having sloping pole faces thereon, an armature mounted on said bimetal adjacent said magnet yoke having one end disposed adjacent said trip member, the other end of said armature being adapted to be attracted against said pole faces in response to overload currents above said predetermined value, spring means mounting said armature on said bimetal element for floating movement relative to said magnet yoke, said armature pivoting about the ends of said pole pieces and causing said one end to engage and actuate said trip member upon movement by said armature against said pole faces.

3. A circuit breaker having relatively movable contacts and a member releasable to effect opening of said contacts, a trip member movable to effect release of said releasable member, a bimetal element operable in response to overload currents below a predetermined value to move said trip member, a U-shaped magnetic member rigidly mounted on said bimetal element and surrounding three sides thereof, the legs of said U-shaped magnetic member forming pole pieces having sloping pole faces thereon, a spring having one end mounted on said bimetal element adjacent said U-shaped magnetic member, an armature mounted on the other end of said spring having one end disposed adjacent said trip member and the other end disposed to be moved toward said pole faces in response to overload currents above said predetermined value, and said armature pivoting about said pole pieces to cause said one end to engage and move said trip member upon movement of the other end of said armature toward said pole faces.

4. A circuit breaker having relatively movable contacts and a member releasable to efiect opening of said contacts, a trip member movable to e fieot'release of said releasable member, a bimetal element operable in response to overload currents below a predetermined value to move said trip member, an adjusting screw on said bimetal element for engaging and moving said trip member upon operation of said bimetal element, a U-shaped'magnetic member rigidly mounted on said bimetal element and surrounding three sides thereof, the legs of said U-shaped magnetic member forming pole pieces having sloping pole faces thereon, a spring having one end mounted on said bimetal element adjacent said U-shaped magnetic member, an armature mounted on the other end of said spring having one end disposed adjacent said trip member and the other end disposed to be moved toward said pole faces in response to overload currents above said predetermined value, said adjusting screw being adjustable to vary the thermal tripping time without changing the positions of said bimetal 61cment and said armature, and said armature pivoting about said pole pieces to cause said one end to engage and move said trip member upon movement of the other end of said armature toward said pole faces.

5. A circuit breaker having relatively movable contacts and a member releasable to effect opening of said contacts, a trip member movable to effect release of said releasable member, a bimetal element supported at one end and having the other end free, said bimetal element being responsive to overload currents below a predetermined value to engage and move said trip member, a U-shaped magnetic member mounted on said bimetal element and surrounding three sides thereof, the legs of said U-shaped magnetic member forming pole pieces having sloping pole faces thereon, a spring having one end mounted on said bimetal element adjacent said U-shaped magnetic member, said spring extending toward the free end of said bimetal element and having its other end free, an armature mounted on the free end of said spring and having one end disposed adjacent said trip member, the other end of said armature being adapted to be moved toward said pole faces in response to overload currents above said predetermined value, and said armature pivoting about the ends of said pole pieces to cause said one end to engage and move said trip member upon movement of the other end of said armature toward said pole faces.

6. A circuit breaker having relatively movable contacts and a member releasable to effect opening of said contacts, a trip member movable to effect release of said releasable member, a bimetal element having one end supported and the other end free, said bimetal being operable in response to overload currents below a predetermined value to cause the free end thereof to engage and move said trip member, electroresponsive means comprising a U-shaped magnetic member mounted on said bimetal element, the legs of said U-shaped magnetic member forming pole pieces having sloping pole faces, a leaf spring having one end mounted on said bimetal element adjacent said U-shaped magnetic member, an armature mounted on the free end of said leaf spring having one end disposed adjacent said trip member and the other end disposed to be moved toward said pole faces when said electroresponsive mean is energized in response to overload currents above said predetermined value, said leaf spring supporting said armature in a normal position substantially parallel to the face of said bimetal element and adjacent to the ends of said pole pieces so that upon energization of said electroresponsive means said armature pivots about the ends of said pole pieces and causes said one end thereof to engage and move said trip member.

HILLER D. DORFMAN. WILLIAM D. PATTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,089,716 Smith Aug. 10, 1937 2,184,372 Von Hoorn Dec. 26, 1939 

